Hey dube, SP3000 coverage is for 2'x5' flowering, if 3 units, I'm afraid that a little not enough, you know that usually the par value over 700 is better for plants growing.
If the budget is limited, 3 units can matches 4'x8' tent.
If your wanna get better results, I think 4 units SP3000 will perform better.
You can try SP3000x3 for a round, see the growing, and add the forth SP3000 for upgraded.